Metalized microphone lid with integrated wire bonding shelf

ABSTRACT

A MEMS microphone package and a method of manufacturing a MEMS microphone package having a lid and a substrate cap. The lid includes a wire bonding shelf that provides a surface internal to the MEMS microphone for connection points for internal wire bonds. One or more conductive traces deposited on the bonding shelf are provided to connect internal electronic components via the wire bonds to a substrate cap. The substrate cap is configured to connect to external devices or components. The internal electronic components include a MEMS microphone die and an application specific integrated circuit. The internal electronic components are configured to transmit signals to external electronics indicative of acoustic energy received by the MEMS microphone die by the configurations described herein.

RELATED APPLICATIONS

The present patent application claims the benefit of prior filed U.S.Provisional Patent Application No. 62/076,084, filed on Nov. 6, 2014,and prior filed U.S. patent application Ser. No. 14/703,233, filed May4, 2015, the entire contents of which are hereby incorporated byreference.

BACKGROUND

Embodiments of the present invention relate to microelectricalmechanical(MEMS) microphone packages and methods of their construction.

SUMMARY

In one embodiment, the invention provides a microelectricalmechanical(MEMS) microphone package including a substrate cap having an interiorand exterior surface. The MEMS microphone package also including amolded lid having an interior and exterior surface attached to thesubstrate cap such that the substrate cap and the lid form a cavity inthe MEMS microphone package. The lid has an acoustic porthole and a MEMSmicrophone die positioned proximal to the porthole. A bonding shelf is amolded structure located within a portion of the cavity. The bondingshelf includes a first electrical trace deposited on the bonding shelf.The first electrical trace has a first end connected to a bonding wireand a second end connected to a contact pad on an interior surface ofthe substrate cap.

In another embodiment the invention provides a method of constructing aplurality of MEMS microphone packages by forming a plurality of lids ona first array, each of the plurality of lids having an acoustic portholeand a wire bonding shelf. The wire bonding shelf including conductivetraces that extend from an internal surface within the MEMS microphonepackage to a substrate cap connection point. A plurality of substratecaps are formed on a second array. Epoxy is deposited on a portion of aninterior surface of each of the lids and a MEMS microphone die and anapplication specific integrated circuit (ASIC) die is fixed to each ofthe lids with the epoxy. The epoxy is then cured. The MEMS microphonedie and the ASIC die are connected such that the ASIC die is connectedto at least one of the conductive traces with wire bonds. The methodincludes connecting the first array and the second array such that thesubstrate cap connection points connect to respective substrateconnection pads for each of the plurality of lids. The combination ofthe lids and substrate caps are singulated to form a plurality ofindividual MEMS microphone packages.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom view of a lid of a MEMS microphone package withoutinternal electronic components.

FIG. 2 is a cross-sectional view of the lid of FIG. 1 along a line A-A.

FIG. 3 is a cross-sectional view of the lid of FIG. 1 along a line B-B.

FIG. 4 is an end view of the lid of FIG. 1.

FIG. 5 is a top-view of the lid of FIG. 1

FIG. 6 is a perspective view of the lid of FIG. 1.

FIG. 7 is an alternate perspective view of the lid of FIG. 1.

FIG. 8 is a bottom-view of a lid of a MEMS microphone package includinginternal electronic components.

FIG. 9 is a cross-sectional view of the lid of FIG. 8 along a line A-A.

FIG. 10 is a cross-sectional view of the lid of FIG. 8 along a line D-D.

FIG. 11 is a perspective view of the lid of FIG. 8.

FIG. 12 is an alternate perspective view of the lid of FIG. 8

FIG. 13 is a bottom-view of a lid of a MEMS microphone package includinga protective coating for wire bonds.

FIG. 14 is a cross-sectional view of the MEMS microphone package of FIG.13 along a line D-D.

FIG. 15 is a perspective view of the MEMS microphone package of FIG. 13.

FIG. 16 is an alternate perspective view of the MEMS microphone packageof FIG. 13.

FIG. 17 is a bottom-view of a substrate cap for a MEMS microphonepackage.

FIG. 18 is a top-view of the substrate cap of FIG. 17.

FIG. 19 is a cross-sectional view of an assembled MEMS microphonepackage.

FIG. 20 is a perspective view of the assembled MEMS microphone packageof FIG. 19.

FIG. 21 is an alternate perspective view of the assembled MEMSmicrophone package of FIG. 19.

FIG. 22 is a top-view of a lid array.

FIG. 23 is a bottom-view of the lid array of FIG. 22.

FIG. 24 is a bottom-view of a substrate cap array.

FIG. 25 is a top-view of the substrate cap array of FIG. 24.

FIG. 26 is a flowchart illustrating a manufacturing method to constructa plurality of MEMS microphone packages.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

In one embodiment, a microelectricalmechanical (MEMS) microphone packageincludes a cavity in the interior of the microphone package. An acousticport in the microphone package allows acoustic pressure (i.e., sound) toenter the microphone package. A MEMS microphone die detects the acousticpressure and coverts the acoustic pressure into an electrical signal.The electrical signal is representative of the acoustic pressurereceived at a diaphragm of the MEMS microphone die. An applicationspecific integrated circuit (ASIC) receives the signal from the MEMSmicrophone die and processes the signal. The output of the ASIC istransmitted via conduction paths to a substrate that forms a cap on theMEMS microphone package.

Original equipment manufacturers produce MEMS microphone packages in avariety of configurations. Among these configurations are top-port andbottom-port designs. In a top-port design, the acoustic port is formedin a top surface of the microphone package. In this design, the topsurface of the MEMS microphone package consists of a lid of the MEMSmicrophone package. In the bottom-port design, the acoustic portpenetrates the bottom surface of the MEMS microphone package. The bottomsurface being the substrate that forms a cap of the MEMS microphonepackage. The following description provides detail of top-ported designsof a MEMS microphone package. However, the design may also beimplemented in bottom-ported designs.

FIGS. 1-7 illustrate multiple views of an embodiment of a lid 100 of aMEMS microphone package. These views illustrate the lid 100 prior tomounting of internal components and prior to attachment of a cap (e.g.,substrate). FIG. 1 illustrates an internal-view of the lid 100. The lid100 includes an interior surface 105 and an exterior surface (shown inFIG. 5). The lid 100 also includes side walls 110. A bonding shelf 115is positioned in one corner of the lid 100. The bonding shelf 115 may beintegrated with the lid as a contiguous molded piece. At least oneconductive trace 120 is deposited on the bonding shelf 115. Theconductive trace 120 extends along an upper surface 125 of the bondingshelf 115 to a lower surface 130 of the bonding shelf 115. The lid 100also includes a conductive surface 135 deposited on a top edge of theside walls 110. An extended conductive trace 140 on the bonding shelf115 extends to the conductive surface 135. The extended conductive trace140 forms an electrical connection with the conductive surface 135.

The interior surface 105 includes a porthole 145 that passes through thelid 100. A conductive ring 150 is deposited on the interior surface 105radially around the porthole 145. A conductive trace 155 is alsodeposited on the interior surface 105 and connected to the conductivering 150. The conductive ring 150 and the conductive trace 155 provideadditional electrical contact points for internal components of the lid100.

FIG. 2 is a cross-sectional view of the lid 100 along the lines A-A.FIG. 2 illustrates a difference in depth between the upper surface 125and the lower surface 130 of the bonding shelf 115. The conductive trace120 and the extended conductive trace 140 extend from the upper surface125 to the lower surface 130 forming a contiguous conduction path fromthe upper surface 125 to the lower surface 130. As also illustrated inFIG. 2, the porthole 145 passes through the lid 100 and flares outwardtowards the exterior resulting in a larger diameter porthole on theexterior surface. Thus, the porthole 145 is tapered inward to funnelacoustic energy toward internal components. The porthole 145 may beformed during the molding process of the lid 100. Alternatively, theporthole 145 may be machined into the lid 100 after the molding process.

FIG. 3 is a cross-sectional view of the lid 100 along the lines B-B. Asillustrated in this view, the bonding shelf 115 may have a smooth,curved transition between the upper surface 125 and the lower surface130. Therefore, the conductive trace 120 and the extended conductivetrace 140 also follow a smooth, curved surface between the upper surface125 and the lower surface 130. Alternatively, the conductive trace 120and the extended conductive trace 140 may follow a flat-sloped or othernon-curved surface of the bonding shelf 115. A space above the lowersurface 130 and between the lower surface 130 and the substrate (notshown) provides space to house wires and connection points for internalcomponents.

FIG. 4 is an end view of the lid 100 of FIG. 1. In this embodiment, theside surface 465 is constructed of molded plastic and is non-conductive.A semi-cylindrical conductive via 470 forms an indent in one or more ofthe side walls 110 of the lid 100. The via 470 includes a conductivecoating on the inside surface of the via 470 such that the via 470 formsa conductive path between the exterior, bottom surface 260 and theconductive surface 135.

FIG. 5 is an external, top-view of the lid 100. Unlike the side surface465, the bottom surface is covered with a conductive layer 260. Theconductive layer 260 may be a metal deposited on or otherwise formed onthe plastic mold. The conductive layer 260 may extend into the porthole145. Thus, the conductive layer 260 may form an electrical connectionwith the conductive ring 150 inside the lid 100. The conductive layer260 may be set to ground potential by the electrical connection thoughthe porthole 145. In this way, the conductive layer 260 forms a portionof a grounded faraday cage to block electromagnetic interference.

FIGS. 6 and 7 are perspective views of the lid 100 as shown in FIGS.1-5. These perspective views provide integrated views of FIGS. 1-5 fromtwo different viewing angles to aid in understanding of the structure ofthe lid 100. It should be noted that the lid 100 may be molded of anon-conductive, plastic material. In other embodiments, the lid 100 maybe manufactured of other non-conductive materials and machined ratherthan molded. In some embodiments, the bonding shelf 115 is not molded aspart of the lid 100, but rather is attached after the lid 100 has beenmolded.

FIGS. 8-12 illustrate a lid 800, which includes the lid 100 and internalelectrical components. As illustrated in FIG. 8, a MEMS microphone die805 and an ASIC die 810 are attached to the interior surface 105 of thelid 800. The MEMS microphone die 805 is positioned proximal to the ASICdie 810 to provide for convenient electrical connections. One or morewires 812 extend from the MEMS microphone die 805 to the ASIC die 810.The wires 812 are attached to contact points 815 on the MEMS microphonedie 805 and contact points 820 on the ASIC die 810. A ground wire 825 ispositioned between the ASIC die 810 and the conductive trace 155. Theconductive trace 155 and the conductive ring 150 (shown in FIG. 1) thusprovide ground connections to the MEMS microphone die 805 and the ASICdie 810. One or more wires 830 are positioned between one or morecontact points 835 on the ASIC die 810 and at least one conductive trace120 on the bonding shelf 115. In addition, a wire 830 is connected tothe extended conductive trace 140 to provide an electrical link betweenthe ASIC die 810 and the conductive layer 260.

FIG. 9 is a cross-sectional view of the lid 800 along a line A-A. TheMEMS microphone die 805 is positioned to cover the porthole 145. Thispositioning ensures that acoustic pressure entering the porthole 145 isdirected to the diaphragm in the MEMS microphone die 805. FIG. 10illustrates a cross-sectional view of the lid 800 along line D-D. Thisview illustrates the connections of the wires 830 to the conductivetrace 155 on the bonding shelf 115. FIGS. 11 and 12 are perspectiveviews of the lid 800 further illustrating the structure of the lid 800.

FIGS. 13-16 illustrate an embodiment of a lid 1300. In particular, FIGS.13-16 illustrate the lid 800 with an additional feature. As illustratedin FIG. 13, a protective coating 1305 covers an end of the wires 830 andcovers a portion of the conductive trace 120 and the extended conductivetrace 140. The protective coating 1305 extends perpendicular to theconductive trace 120 to form a protective strip that provides protectionto the wire bonds between the conductive trace 120 and the wires 830.The protective coating 1305 may take various forms and may be formed ofvarious materials. As illustrated in FIG. 14, the protective coating1305 is a non-conductive glue or epoxy resin that is applied after thewires 830 are soldered to the conductive trace 120. In otherembodiments, the protective coating 1305 may be a non-conductive solidpiece of material affixed to the bonding shelf 115. In otherembodiments, the protective coating 1305 may not be continuous acrossthe wires 830. For example, the protective coating 1305 may take theform of individual drops or separate pieces of material positioned oneach of the solder connections between the wires 830 and the conductivetrace 120. FIGS. 15 and 16 are perspective views that illustrate thepositioning of the protective coating 1305. In some embodiments, theprotective coating 1305 may be made of temperature resistant material.For example, the protective coating 1305 may be glue with a meltingpoint well above the melting point of solder.

FIG. 17 is an illustration of a substrate 1700 on an external side 1705.The substrate 1700 may be formed of various materials, for example,laminate printed circuit board (PCB), ceramic, or polyimide. Theexternal side 1705 includes electrical contact pads (e.g., land gridarray (LGA) pads) 1710 that provide for electrical connection with otherdevices. As illustrated in FIG. 18, the contact pads 1710 are routed viatraces 1810 on or in the substrate 1700 to a package side 1805 of thesubstrate 1700. The traces 1810 connect to input/output pads 1815 on thepackage side 1805 of the substrate 1700. The input/output pads 1815 arealigned to mate with the conductive trace 120 and the extendedconductive trace 140 on the upper surface 125 of the bonding shelf 115.Signals from the MEMS microphone die 1805 and the ASIC 1810 aretransmitted via the conductive trace 120 to the contact pads 1710.Another electrical contact surface 1820 is provided along the perimeterof the package side 1805 of the substrate 1700. In alternativeembodiments, the contact pads 1710 may use other surface mounttechnologies.

FIGS. 19-21 illustrate an assembled MEMS microphone package 1900including the lid 100, 800, 1300 and the substrate 1700. In particular,FIG. 18 is a cross-sectional view of the MEMS microphone package 1900.As illustrated, the electrical contact surface 1820 on the substrate1700 mates with the conductive surface 135 on the lid 100. Theelectrical contact surface 1820 presses against the conductive surface135 and forms an airtight seal 1905 to prevent material or sound fromentering the MEMS microphone package 1900 at the seal 1905. FIGS. 20 and21 are perspective views of an assembled MEMS microphone package 1900.In particular, FIG. 20 illustrates the substrate 1700 of the MEMSmicrophone package 1900 and FIG. 21 illustrates the lid 100 of the MEMSmicrophone package 1900.

FIGS. 22-25 illustrate components of the MEMS microphone package 1900arranged in an integrated array. FIG. 22 illustrates a top-view of a lidarray 2200 including a plurality of lids 2205 prior to singulation. Theplurality of lids 2205 including the lid 100. The illustration of thelid array 2200 includes the porthole 145 and the conductive via 470.FIG. 23 illustrates an internal view of the lid array 2200 (i.e.,bottom-view). FIG. 24 illustrates an external view (i.e., bottom-view)of a substrate array 2400 including the contact pads 1710. FIG. 25illustrates an internal view (i.e., top-side) of the substrate array2400 including the conductive traces 1820 and the input/output pads1815.

The substrate 1700 is attached to the conductive surface 135 at the seal1905. The seal 1905 may be formed with solder, which mechanically andelectrically connects the substrate 1700 with the conductive surface135. During the soldering process, excess solder or heat may damage theconnections between the wires 830 and the conductive trace 120 and theextended conductive trace 140. The protective coating 1305 prevents theexcess solder or heat from directly contacting the wire bondconnections. In this way, the bonding shelf 115 provides a surface forglue or similar material to create a solder resist layer that protectswire bonds from subsequent solder-based assembly steps.

FIG. 26 is a flowchart illustrating a method 2600 of manufacturing theMEMS microphone package 1900. According to the method 2600, theplurality of lids 2205 is formed as an array 2200 (step 2605). Epoxy isplaced in each of the plurality of lids 2205 on the interior surface 105where the MEMS microphone die 805 and the ASIC die 810 will bepositioned (step 2610). For each lid 100 of the plurality of lids 2205,the MEMS microphone die 805 and the ASIC die 810 are positioned on theepoxy and the lid array 2200 is cured (step 2615). The wires 812, theground wire 825, and the wires 830 are bonded to the contact pads 880,the conductive trace 855, the contact pads 875, and the contact pads 890of each of the plurality of lids 2205 (step 2620). The protective layer(e.g., epoxy bead) is dispensed on the bonding shelf 115 of each of theplurality of lids 2205, and if epoxy is used, cure (step 2625). Dispensesolder or epoxy on the substrate array 2400 such that the solder orepoxy aligns with the conductive surface 135 of each of the plurality oflids 2205 (step 2630). Align and position the substrate array 2400 ontothe lid array 2200 and either reflow the solder or cure the epoxy (step2635). Singulate (e.g., saw) the combination of the lid array 2200 andthe substrate array 2400 into each MEMS microphone package 1900 (step2640).

In the method 2600, covering the bonding shelf 115 with the protectivelayer in step 2625 protects the wire bonds that are performed in step2620. In this way, the wire bonds are protected from solder wettingperformed in subsequent steps. Therefore, the conductive trace 120 andthe extended conductive trace 140 may be connected to the input/outputpads 1815 without the use of a solder mask.

Thus, the invention provides, among other things, a plurality of MEMSmicrophone packages each having a lid and a substrate cap. The lidincludes a wire bonding shelf that provides a surface internal to theMEMS microphone for connection points. One or more conductive tracesdeposited on the bonding shelf connect internal electronic componentswith a substrate cap. Various features and advantages of the inventionare set forth in the following claims.

What is claimed is:
 1. A method of manufacturing a plurality of MEMS microphone packages, the method comprising: forming a plurality of lids on a first array, each of the plurality of lids having an acoustic porthole and a wire bonding shelf, the wire bonding shelf including conductive traces that extend from an internal surface within the MEMS microphone package to a substrate cap connection point; forming a plurality of substrate caps on a second array; connecting the first array and the second array such that the substrate cap connection point connects to a respective substrate connection pad for each of the plurality of lids; and singulating the plurality of lids and the plurality of substrate caps such that a plurality of individual MEMS microphone packages are formed.
 2. The method of claim 1, the method further comprising connecting a MEMS microphone die and an ASIC die to each of the plurality of lids on the first array.
 3. The method of claim 2, the method further comprising electrically connecting the MEMS microphone die to the ASIC die and the ASIC die to at least one of the conductive traces with wire bonds.
 4. The method of claim 1, the method further comprising: depositing epoxy on a portion of an interior surface of each of the lids; fixing a MEMS microphone die and an ASIC die to each of the lids with the epoxy; and curing the epoxy.
 5. The method of claim 1, the method further comprising dispensing a protective coating on a portion of the bonding shelf such that connection points on the conductive traces are protected.
 6. The method of claim 5, wherein the protective coating is made from epoxy.
 7. The method of claim 5, wherein the protective coating forms a nonconductive strip across the conductive traces.
 8. The method of claim 5, wherein the protective coating protects the connection points from heat and solder.
 9. The method of claim 1, wherein the first array and the second array are connected with an airtight solder seal around a perimeter of each of the plurality of lids.
 10. The method of claim 9, wherein the first array and the second array are connected with an epoxy seal. 